This invention relates to a camera shutter for enabling a shutter blade to be opened and closed by a step motor.
The camera shutter for enabling a shutter blade to be opened and closed by the step motor is constituted in such that drive pulses having a fixed frequency is input to the step motor by a release operation to forwardly rotate the step motor and to gradually open sectors, and a phase of the drive pulse is switched at a timing when the step motor is rotated by such steps corresponding to an exposure quantity to reversely rotate the step motor and to close the sectors, thus obtaining a predetermined exposure.
However, in such a shutter enabling sectors to be opened and closed by the step motor as above mentioned, synchronization between a rotational phase of a rotor and a drive pulse tends to fail because of fluctuation in load torque of a shutter mechanism itself, and there occurs a dislocation in rotaton of the rotor to disadvantageously cause the shutter to remain open.